The present invention relates generally to mode selection control of air conditioning units, for example room-sized combination heating and cooling units. More particularly, the invention relates to such control systems having both relatively local mode selection capability and relatively remote mode selection capability, for example, from a central control desk of a hotel, office building, or the like.
A common configuration for a building heating and cooling system employs an individual air conditioning unit in each room of a hotel, office building, or the like, with individual room thermostatic and mode selection control. Such a system desireably facilitates zoned temperature control. That is, the temperature of each room may individually be adjusted as desired. Further, such a system permits overall economy of operation where not all rooms are occupied or in use at the same time. Unneeded units may simply be turned off.
A wide variety of specific types of air conditioning units have been employed for such purposes, and there is accordingly no intention to limit the present invention for use in combination with any particular such unit. Similarly, the term "air conditioning" is employed herein in a broad sense to mean any form of unit which alters the characteristics of room air, for example by either heating, cooling, or both, or even through humidity modification. As one example, a typical such room sized unit includes an air cooling portion comprising a closed circuit refrigeration system having a refrigerant evaporator in heat exchange relationship with recirculating indoor air flow, and a separate heating portion comprising electrical resistance heaters. As another example, the closed circuit refrigeration system may be reversible and comprise what is conventionally termed a "heat pump" to provide heating, as well as cooling, with electrical resistance heating being required only for supplemental purposes. Also, a reversible air valve heat pump may be employed, where the evaporator and condenser retain their usual functions relative to the closed circuit refrigeration system, but indoor and outdoor airflows are selectively directed over the evaporator and condenser. Still other examples are radiator-like room-sized units which receive a circulating heat transfer medium such as heated or cooled water from a central location, and which include controlled valving or fan arrangements for regulating the amount of heating or cooling delivered to a particular room. It will be appreciated that such units are typically capable of various modes of operation. In addition to "heating" mode, "cooling" mode, and "off" mode, various other modes such as "high" and "low" fan speeds are frequently provided.
For selecting these various modes, different forms of mechanical selector switches have heretofore been employed, usually located on each individual room unit itself. Two common control configurations are a rotary detent-type switch and a interlocked mechanical push button arrangement with exclusive selection capability arranged such that, when a desired selection push button is depressed to complete a circuit to effect the particular function desired, all of the remaining push buttons automatically pop up.
As mentioned hereinabove, where various rooms are unoccupied or not in use at any particular time, energy savings and overall economy of operation can result where units are turned off when not needed. Examples are office buildings during the evenings and weekends, and hotel rooms any time a particular room is unoccupied.
Advantageously, central desk or remote control systems have heretofore been employed such that an attendant at the central desk of a hotel or the like can turn off units in unoccupied rooms, and turn on such units when a room is to be occupied. Similarly, in an office building, all units can be turned off during evenings and weekends. A typical such prior art system comprises a relatively simple control relay arrangement including a power relay to each air conditioning unit, with each relay having switching contacts in series with the line power supply to the particular individual unit. The central desk than has control over relay operation.
However, the limited capabilities of such a system result in a number of disadvantages. In particular, with such a prior art system, the basic mode selection is made at the room unit itself by means of a mechanical selector switch, and the central desk control can only turn the unit on or off. Moreover, if a particular unit is turned off at the central desk, it will normally not be possible to energize the unit at the location of the air conditioning unit itself, as might occur where a desk attendant inadvertently fails to reactivate a particular unit.